The Scottish Premier League outfit had been hoping to snap up the 21-year-old this summer.
However, having enjoyed an impressive end to the 2010/11 campaign, interest in Forsyth's services has suddenly grown.
And Saints boss Derek McInnes admits that the youngster is now unlikely to remain in Scotland.
"We offered Craig a three-year contract which he was happy with," McInnes told The Courier.
"But he wanted to wait until the end of the season before making a decision and, the way his season has finished, there has been a lot of interest in him.
"Unfortunately, that's probably counted against us and we might now lose out on him - but the offer's still there."